Electrical Trade Theory N2

TVET FIRST

Electrical Trade Theory N2

This document includes important informa on about the revised curriculum for Electrical Trade Theory N2, scheduled for implementa on in 2021. Contact jayshil.bhula@macmillaneduca on.co.za to request a sample copy of the TVET First approved textbook or visit our website at www.macmillaneduca on.co.za. For best results, use TVET First Electrical Trade Theory N2!

Changes to the curriculum for 2021:

• The curriculum has been revised and updated. • All Learning Outcomes have been renumbered and rewri en. • There is more content covered than before. • The curriculum has now been broken into 11 modules instead of 9. • New modules on AC theory, electrical re cula on, ba eries and renewable energy. • Electronics is no longer part of this curriculum.

Modules and weigh ngs:

The new curriculum has been broken down into modules with weigh ngs as follows:

New curriculum (2021):

Calcula on ques ons Theory and drawing type ques ons

Module 1 Alterna ng current circuit theory 7% 5%

Module 2 Conductors, insulators and cables 3% 9%

Module 3 Electrical re cula on 0% 8%

Module 4 Switchgear and Protec ve devices 0% 10%

Module 5 Ba eries 0% 10%

Module 6 Direct current machines 0% 10%

Module 7 Alterna ng current machines 0% 8%

Module 8 Transformers 5% 5%

Module 9 Earthing 0% 10%

Module 10 Measuring instruments 3% 3%

Module 11 Renewable energy 0% 4%

Total weight

12%

12%

8%

10%

10%

10%

8%

10%

10%

6%

4%

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Summary of the changes

Overview/highlights:

• New module on AC theory (12% weigh ng) includes: – Dynamically induced emf and sinusoidal waveforms, three-phase circuits moved here from the old N1 curriculum – Brand new LOs on sta cally induced emf • Conductors insulators and cables – PVC insulated, wire armoured cables; PILCSTA and PILCSWA and XLPE cables moved here from the old N1 curriculum • Electrical re cula on has been given its own module with Learning Outcomes on the networks, genera on, transmission and distribu on (8% weigh ng) • The switchgear and protec ve devices have been reduced in weight from 22% to 8% – Circuit breakers are covered in less detail in the switchgear module – Day night switches and mers have been added to the switchgear module • New module on ba eries (10% weigh ng) includes: – Lead acid ba eries, rela ve density, capacity, tes ng moved here from old N1 curriculum – Brand new LOs on gel ba eries and lithium ba eries • Direct current generators have been moved into this curriculum (DC machines module) from the old

N1 curriculum (opera on and commuta on). The learning content for DC motors is largely unchanged • AC machines have been reduced from 15% to 8% weigh ng – Starters for AC motors are no longer covered in the N2 curriculum – Split phase motors and shaded pole motors are now included under single phase motors as well as reversing direc on of single phase motors – Applica ons of the diff erent single and three-phase motors now included • Electronics has been removed completely

Details of curriculum changes:

Module 1 [NEW MODULE in N2]

Weight 12% (not previously covered in N2)

CHANGES

ALTERNATING CURRENT CIRCUIT THEORY (This topic was previously covered in Electrical Trade Theory N1)  Includes theory and calcula ons

New learning content on: • Dynamically induced emf (previously covered in N1) – Calculate the magnitude

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Module 2

[Old Module 1] New weight 12% Old weight 11 %

Module 3 [NEW MODULE in N2]

Weight 8% (formed small part of Module 4 previously)

CHANGES

– Includes sinusoidal waveforms, instantaneous, average, maximum, eff ec ve values, form factor • Sta cally induced emf (NEW to N2) • The power triangle and power factor (previously covered in Transformer Module 8 and cable module) • Three-phase circuits (star and delta connected systems) (previously covered in N1)

CONDUCTORS, INSULATORS AND CABLES (This was Module 1 in the old curriculum; some of this content has been moved from N1 to N2)  Includes theory and calcula ons

• New learning content on: – Conductors and insulators (previously covered in N1 only – now in both) – Cable defi ni ons – PVC insulated, wire armoured cables; PILCSTA and PILCSWA and XLPE cables (previously covered in N1) – Cable joints (previously covered in the switchgear module) • Content remaining: – Selec ng cables – Installing cables – Calcula ons related to selec ng and installing cables (voltage drop, current drawn by load, maximum prospec ve short-circuit current); infl uence of inductance – Regula ons rela ng to cables and cable termina ons and cable joints

ELECTRICAL RETICULATION (Previously covered briefl y in the switchgear module, now given more prominence in its own module)  Theory only

• New learning content on: – Re cula on networks, genera on, transmission and distribu on (previously in switchgear module in less detail) – Feeder systems

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Module 4

Weight 10% (Reduc on in weigh ng – the old Module 4 and Module 6 combined were weighted 22%)

Module 5 [NEW MODULE in N2]

Weight 10% (not covered in N2 previously)

Module 6

New weight 10% (Old weight 12%)

CHANGES

SWITCHGEAR AND PROTECTIVE DEVICES (This module combines the old Module 4 and the old Module 6)  Theory only New learning content on:

• Switchgear purpose and func on • Timers and day night switches have been added to devices for isola ng, control and protec on • Overload protec on has been moved here from the AC machine module

Content remaining:

• Disconnectors, relays and contactors • Over current and earth leakage protec on

No longer covered:

• Circuit breakers are covered in less detail • Electrical re cula on moved to Module 3 • Cable joints moved to Module 2

BATTERIES (This topic was previously covered in N1)  Theory only. This new module covers half of the old N1 material (that wasn’t covered in the new N1) plus some new outcomes.

• New learning content on: – Lead-acid ba eries (construc on, opera on, care and maintenance) (previously in N1) – Rela ve density, capacity, tes ng (previously in N1) – Gel ba eries (construc on, applica on, charging, care and maintenance) (NEW) – Lithium-ion ba eries (construc on, opera on, care and maintenance) (NEW)

DIRECT CURRENT MACHINES (This was previously Module 3 + DC generators which were previously covered in N1)  Theory only. New learning content on:

• Opera on of DC generators and commuta on (NEW in N2 – previously covered in N1)

Content remaining:

• Construc on of DC machine, armature assembly, brush gear • Compare diff erent motors (shunt, series and compound-wound)

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Module 7

New weight 8 % (Old weight 15%)

Module 8

New weight 10% (Old weight 12%)

CHANGES

• Draw circuit diagrams of DC motors • Faceplate starter for DC motor • Reversal of direc on of DC motor

ALTERNATING CURRENT MACHINES (This was previously Module 4)  Theory only New learning content on:

• Single phase motors: – Split phase motors – Shaded pole motors – Applica ons of all listed single phase motors – Reversing direc on of rota on • Three phase induc on motors: – Connec on of stator windings – Applica ons

Content remaining:

• Single phase motors (construc on and opera on): – Capacitor start/induc on run – Capacitor start/capacitor run – Universal • Three phase induc on motors: – Construc on and opera on • Comparing advantages and disadvantages of single vs three phase motors • Tes ng of single phase and three phase induc on motors

No longer covered:

• Starters for AC motors are no longer covered in N2 (moved to N3) • Overload protec on is now covered in Module 4 on Switchgear

TRANSFORMERS  Includes theory and calcula ons New learning content on:

• Construc on and opera on of a single phase transformer (previously covered in N1) • Calculate turns ra o of ideal transformer - single and three phase (single phase previously covered in N1) • Equivalent circuit diagram and vector diagram of transformer on no load (NEW in N2)

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Module 9

New weight 10%

Module 10

New weight 6% (Old weight 6%)

CHANGES

• State func on of and calculate magne sing and core-loss components of no-load current from no-load vector diagram (NEW in N2) • Distribu on transformer use in residen al areas (NEW in N2)

Content remaining:

• Func on of a transformer in terms of current and voltage • Turns ra o and related voltage and current calcula ons • Calculate the ra ng of ideal transformer (single and three phase) and state why transformers are rated in kW • Three phase transformer confi gura ons, calcula ons and circuit diagrams

No longer covered:

• Types of power, power triangle and power factor + calcula ons have been moved to

Module 1 • Transformer tappings are no longer covered in N2

EARTHING (This was previously Module 5)  Theory only Content remaining:

• Earthing and the earthing chain, earthing of underground cables, fl oa ng earth, bonding to earth, touch voltage • Earthing of overhead lines

No longer covered:

• System and equipment earthing/protec ve earthing has been removed and moved to N3 • Earthing at power sta ons moved to N3 • Insula on of cable glands not covered

MEASURING INSTRUMENTS  Includes theory and calcula ons New learning content on:

• Range extension of galvanometers (NEW in N2) • Digital measuring instruments (NEW in N2)

Content remaining:

• How measuring instruments are connected to a low-voltage circuit and a high-voltage circuit (previously covered par ally in N1 and also in N2) • The func on of diff erent measuring instruments has been removed from the curriculum

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Module 11 [NEW MODULE in N2]

Weight 4%

CHANGES

No longer covered:

• Principle of opera on of the insula on resistance tester (Megger) is no longer covered

RENEWABLE ENERGY  Theory only New learning content on:

• How renewable energy is used to produce electricity • Layout of a typical power plant using renewable energy sources

TVET First author:

Sunil Chuturgoon